--no-clean option for kdist build (#4583)

fixes: #4481 

By default, `kdist` will delete the output folder of a target before
building it. This adds a `--no-clean` option to `kdist build` which will
be useful for keeping the parse cache of a kompiled semantics when
rebuilding.

pyk/src/pyk/kdist/__main__.py

@@ -48,13 +48,15 @@ def _exec_build(
     force: bool,
     verbose: bool,
     debug: bool,
+    clean: bool,
 ) -> None:
     kdist.build(
         target_ids=_process_targets(targets),
         args=_process_args(args),
         jobs=jobs,
         force=force,
         verbose=verbose or debug,
+        clean=clean,
     )
 
 
@@ -130,6 +132,9 @@ def add_target_arg(parser: ArgumentParser, help_text: str) -> None:
     )
     build_parser.add_argument('-f', '--force', action='store_true', default=False, help='force build')
     build_parser.add_argument('-j', '--jobs', metavar='N', type=int, default=1, help='maximal number of build jobs')
+    build_parser.add_argument(
+        '--no-clean', dest='clean', action='store_false', default=True, help="Don't clean before building"
+    )
 
     clean_parser = command_parser.add_parser('clean', help='clean targets')
     add_target_arg(clean_parser, 'target to clean')

pyk/src/pyk/kdist/_kdist.py

@@ -86,6 +86,7 @@ def build(
         jobs: int = 1,
         force: bool = False,
         verbose: bool = False,
+        clean: bool = True,
     ) -> None:
         args = dict(args) if args else {}
         dep_ids = target_cache().resolve_deps(target_ids)
@@ -108,6 +109,7 @@ def submit(target_id: TargetId) -> None:
                     args=args,
                     force=force,
                     verbose=verbose,
+                    clean=clean,
                 )
                 pending[future] = target_id
 
@@ -134,6 +136,7 @@ def _build_target(
         *,
         force: bool,
         verbose: bool,
+        clean: bool,
     ) -> Path:
         target = target_cache().resolve(target_id)
         output_dir = self._target_dir(target_id)
@@ -145,8 +148,9 @@ def _build_target(
             if not force and self._up_to_date(target_id, manifest):
                 return output_dir
 
-            shutil.rmtree(output_dir, ignore_errors=True)
-            output_dir.mkdir(parents=True)
+            if clean:
+                shutil.rmtree(output_dir, ignore_errors=True)
+            output_dir.mkdir(parents=True, exist_ok=True)
             manifest_file.unlink(missing_ok=True)
 
             with (
@@ -156,7 +160,8 @@ def _build_target(
                 try:
                     target.target.build(output_dir, deps=self._deps(target), args=args, verbose=verbose)
                 except Exception as err:
-                    shutil.rmtree(output_dir, ignore_errors=True)
+                    if clean:
+                        shutil.rmtree(output_dir, ignore_errors=True)
                     raise RuntimeError(f'Build failed: {target_id.full_name}') from err
 
             manifest_file.write_text(json.dumps(manifest))